1,2,3,4-Tetrachlorohexafluorobutane is a compound which is important as a synthetic raw material etc. for hexafluoro-1,3-butadiene attracting attentions as an etching gas used for fine process of semiconductors. A process described in the following patent document has so far been known as a production process for 1,2,3,4-tetrachlorohexafluorobutane.
A process for producing 1,2,3,4-tetrachlorohexafluorobutane by reacting a compound represented by CClX1X2—CClX3—CClX4—CClX5X6 (X is a hydrogen atom or a fluorine atom) with fluorine in a liquid phase is described in Japanese Patent Application Laid-Open No. 2006-342059 (patent document 1). It is described therein that in the above process, a perfluoroalkane, a perfluoroether, a perfluoropolyether, a chlorinated fluorinated hydrocarbon and a perfluoroalkylamine are used as a solvent. The solvent has to be separated from the product, recovered and reused. Also, it is described therein that, when 1,2,3,4-tetrachlorohexafluorobutane is used as a solvent for fluorination reaction, an advantage is obtained that it is unnecessary to separate the solvent from the product, so that it is particularly preferred. However, the fluorination reaction is carried out with low concentrations of the reaction raw materials diluted by the solvent, so that a problem is left in terms of industrially efficiently producing a targeted product.
Further, it is known that optical isomers and a meso form are present in 1,2,3,4-tetrachlorohexafluorobutane, and when various isomers of 1,2,3,4-tetrachlorohexafluorobutane are not distinguished and used as a diluent or a solvent in the form of a mixture, a reaction temperature is set in many cases based on an isomer having a highest melting point among the above isomers. Accordingly, when carrying out a liquid phase reaction, a reaction temperature has to be set at a high temperature to some extent in a certain case in order to carry out the reaction while maintaining a liquid phase. The above manner brings about such a problem that side reactions of producing low boiling fraction and the like by C—C cleavage in fluorination reaction proceed to lower the yield or fluorination goes on in excess.
Further, it is thought as well that provided a product of reaction is used as a solvent, the product is liable to be excessive to the reaction raw material and that reaction of a direction reverse to a direction in which 1,2,3,4-tetrachlorohexafluorobutane is produced is liable to go on in terms of Gibbs's free energy. Accordingly, this allows a problem to be left in the process for producing 1,2,3,4-tetrachlorohexafluorobutane described in the patent document 1 in terms of industrially efficiently producing a targeted product.    Patent document 1: Japanese Patent Application Laid-Open No. 2006-342059